The present invention relates to "yard hostler" tractors for the short-distance movement of normal semi-trailers and, more particularly, to a "yard hostler" tractor which includes equipment so that the tractor is also capable of functioning as a rail bogie handling vehicle in conjunction with dual-mode rail-highway vehicle systems which employ separable rail bogies.
Yard hostler tractors are typically employed at truck and intermodal freight terminals, commonly known as "piggy-back" terminals, to position and/or move semi-trailers which are carried on railroad flat cars. Hostler tractors are used in this context to move trailers to and from parking areas and to locate the trailers near their intended position in the train. Large cranes are used to lift the trailers onto or off of flat cars which comprise the trains. Normally, hostler tractors are employed only within the confines of the terminal and adjacent areas because they are not capable of highway speeds. Further, these tractors are equipped with elevating fifth wheel devices so that trailers may be picked up and dropped off with high efficiency. More particularly, where an elevating fifth wheel is provided, the operator need not exit the cab of the vehicle in order to raise the landing gear of a semi-trailer being handled. Often an openable window or door is provided in the rear of the cab so that the driver can reach outside to connect the normal air brake lines between the tractor and trailer quickly.
Elevating fifth wheel devices on most hostler tractors are either pneumatically or hydraulically operated. The fifth wheel assembly is usually mounted on a forwardly-projecting beam pivoted to the frame of the vehicle adjacent the rear of the cab. Large air springs or hydraulic cylinders are interposed between the beam and the vehicle frame which, when activated, raise the rear of the beam and thus the fifth wheel above a normal or relaxed height. When a trailer is "hitched" on the fifth wheel, activation of the air springs or hydraulic cylinders lifts the nose of the trailer so that it may be moved without retracting its landing gear. On the other hand, when the proper destination is reached, the operator can lower the fifth wheel and thereby set the trailer again onto its landing gear, unlock the fifth wheel from the trailer king pin, disconnect the air brake lines and drive away.
Recently, dual-mode articulated rail-highway vehicle systems which employ separable rail bogies have been developed. In such a system, semi-trailer bodies which have retractable highway wheels are coupled to detachable rail bogies and the vehicles are then coupled end to end so as to form trains. No conventional rail cars are used in this system thereby reducing weight, cost and maintenance. However, as the rail bogies are left behind on the rail when the semi-trailer bodies are taken by normal tractors to their destinations over highway, the need has developed for a vehicle that can handle and transport rail bogies about the railway yard.